We can draw this figure out by using a '-' for a mile of the trail, and a 'l' for a sign. There will not be a sign at the beginning, but there will be a sign at the end. So let's draw that:
-l-l-l-l-l-l-l-l-l-l-l-l-l-l-l-l
By counting the amount of 'l's in the figure above, we are then able to determine that there will be 16 signs posted.
d. since we know it can travel 500 mph and it has enough fuel to fly for another 1500 miles. it can fly for 3 more hours, the reason D is the correct answer is since the plane can't fly more than 3 hours so it will fly for 3 hours exactly or less
